In a first of its kind achievement in India, Thermax has designed a boiler that will generate steam and power using highly polluting distillery waste – spent wash – as fuel. The first such boiler is being commissioned for a distillery in Karnataka.

Distilleries can be highly polluting as 88% of their raw materials result in waste, which is discharged into fields and water bodies. Spent wash is one of the polluting byproducts of the distilling process in molasses based plants. This brownish liquid waste is spewed out in large quantities; a typical distillery generates about 1,000t every day. Earlier, this waste used to be treated by bio-methanation (producing biogas to be used as fuel in boilers) or converted to manure through bio composting. However, both methods have their drawbacks. Large quantities of waste still remains after biogas production, posing a serious threat to local water bodies; and bio-composting is hampered by the requirement of large tracts of land and by rains that spread pollution.

Though Thermax has extensive experience in burning a wide array of waste fuels, spent wash brought its unique set of vexing problems for the boiler and heater group. Besides the high moisture content, spent wash is highly corrosive and contains melting material that makes combustion difficult. These issues were sorted out after extensive R&D trials, and with coal as a support fuel the 23 TPH Thermax boiler will successfully incinerate the spent wash at the Karnataka distillery. An evaporator will concentrate the 1,000t waste to around 200t before it is fed into the boiler. Steam from the boiler will be used in the distillery processes and will also co-generate 2MW of power that would end its dependence on the power grid.

The plant will be commissioned in August and start operations in early September 2008.

By generating steam from spent wash, molasses based distilleries can significantly reduce their energy costs. Every kilogram of concentrated spent wash replaces nearly 0.33kg of Indian coal. The energy savings can pay back the boiler investment in 36 months. Community life around the distillery sites need not be plagued by pollution as the discharge of spent wash is almost entirely eliminated – a relief for the distillery sector in view of growing public awareness and the tightening regulations on pollution control.

In addition, Thermax has already won several other orders from leading distilleries in the country.